The overall objective of this research project is to develop behaviorally based methodologies that will provide clinicians and researchers with new tools for assessing auditory-perceptual processing skills of deaf infants before and at regular intervals following cochlear implantation. A new laboratory has been constructed at the Indiana University School of Medicine to implement two behavioral procedures that have been used extensively by developmental scientists to study speech perception and language development in normal hearing infants. Infants are seated in a sound booth in front of a TV monitor from which auditory and visual stimuli are presented. In the Visual Habituation (VH) procedure, the duration of infants' looking times to a visual display in response to different types of speech sounds is measured. In the Preferential Looking Paradigm (PLP), infants are first presented with two novel-word/novel-object pairings. After exposure, they are then presented with both visual objects and one of the novel words. Their looking times to the two objects is measured to determine if they look longer to the visual object that was paired with the novel word. These two techniques have been adapted and used to test 20 deaf infants before and after implantation in our preliminary studies. We propose to use the VH and PLP to address four specific aims. In Specific Aim 1, we will use VH to assess deaf infants' selective attention and speech discrimination skills before and longitudinally after implantation. In Specific Aim 2, we will use VH to assess deaf infants' sensitivity to language-specific segmental and suprasegmental properties of their native language after several months of experience with a CI. In Specific Aim 3, we will use the PLP to measure and assess deaf infants' word learning skills after several months of CI use. Finally, in Specific Aim 4, we will assess the relations between infants' performance on the above tests and their later speech and language skills at 2 to 4 years of age, which will be measured using traditional clinical outcome measures. The proposed research addresses pressing clinical issues regarding the potential benefits of very early cochlear implantation on deaf infants' speech and language development. These new measures will provide clinicians and researchers with tools for tracking individual infants' progress in acquiring early fundamental auditory and linguistic processing skills that provide the foundation for later speech and language development.